Microstructure and micro-mechanical property evaluation of high-aspect-ratio micro-ribs constructed via elliptical vibration chiseling

Elliptical vibration chiseling (EV-chiseling) is a novel superior process to create micro-ribs on metallic surfaces. However, the formation mechanism and mechanical properties of micro-ribs are still unclear, which hinders its deterministic fabrication. This study concentrates on the formation mechanism clarification and mechanical property characterization of the as-constructed micro-ribs. A mechanistic cutting force model was developed and validated experimentally, revealing that the strain rate in EV-chiseling can reach up to 103 s−1. Crystallographic analysis on the microstructural evolution inside the micro-ribs exhibited that high strain rate deformation induced significant grain refinement, up to 41 times finer than the material matrix. Dislocation analysis further revealed high-density dislocation accumulation and extensive twin formation, contributing to microstructural refinement. As compared to the material matrix, in-situ micro-mechanical testing confirmed substantial improvements in mechanical properties, with hardness and reduced modulus increased by up to 27.4% and 24.2%, respectively. These enhancements were correlated with grain size reduction through the Hall-Petch relationship. The findings bring valuable insights into the interplay between high strain rate deformation, microstructural evolution, and mechanical property enhancement in the EV-chiseling process, and highlight the potential of constructed metallic micro-ribs for improved durability. Furthermore, higher frequency in EV-chiseling process is believed to introduce higher deformation strain rates, more significant grain refinement and more micro-mechanical property improvement.